Cervical Pessary vs Vaginal Progesterone in Preventing Preterm Birth Among Women Presenting With Short Cervix: An Open-label Randomized Controlled Trial

Preterm birth represents a major challenge to obstetricians as well as healthcare policy makers. It is a leading cause of perinatal morbidity and mortality among singleton and multiple pregnancies. In the USA, the frequency of of preterm births (<37 completed weeks of gestation) is 10-13% in singleton pregnancies, and 57% in twins and these rate have not substantially changed in the last decade.

A short cervix (<25 mm) measured by vaginal ultrasonography during mid pregnancy (18-24 weeks of gestation) is a powerful predictor of spontaneous preterm birth (PTB). The relative risk for PTB increases as the cervical length decreases.

The two most studied treatment options in cases of short cervix at mid pregnancy are vaginal progesterone preparations, and cervical cerclage. Vaginal progesterone, given either as 90 mg gel or 200 mg suppository, was repeatedly shown to significantly reduce PTB rates and perinatal morbidity and mortality in women found to have a short cervix (20 mm or less) at 24 weeks gestation.

Progesterone were proven ineffective for the prevention of preterm birth in cases of multiple gestations, present preterm labor, or preterm premature rupture of membranes.

Cerclage may be considered an alternative for vaginal progesterone only in women with history of PTB that are found to have a short cervix in the present pregnancy (cervical length <25 mm before 24 weeks of gestation). According to a recently published indirect meta-analysis, vaginal progesterone and cerclage are equally efficacious in the prevention of PTB in women with a singleton gestation, mid trimester sonographic short cervix, and a history of previous preterm birth.

Unfortunately, vaginal progesterone and cervical cerclage were not proven effective for the prevention of PTB in twin gestations. Moreover, cervical cerclage in this context may even lead to worse outcome compared to conservative treatment. Additionally, in contrast to singleton pregnancies, neither vaginal progesterone nor injections of 17alpha-hydroxyl-progesterone caproate prevented neonatal morbidity or preterm birth in multiple pregnancies. One meta-analysis suggested that vaginal progesterone for mid trimester short cervix in twin gestation may improve neonatal outcome without prolonging the pregnancy.

Cervical Pessary is a renovated method, currently being studied for its clinical advantages over the existing available treatments in the context of midtrimester asymptomatic short cervix in singleton and twin gestation.

The largest multicenter randomized controlled trial (RCT) on pessary use in selected women screened by Trans Vaginal Sonography (TVS) excluded women who had one of the following: a known major fetal anomaly, painful regular uterine contractions, active vaginal bleeding, ruptured membrane, placenta previa, or a history of cone biopsy or cervical cerclage in situ. The conclusion of this study was that in women with a short cervical length (>25mm) between 18-22 weeks, the use of cervical pessary significantly prolonged pregnancy and reduced the rate of poor neonatal outcome compared with control, untreated patients. A second, and smaller, RCT failed to corroborate the findings previously described. In this study, the mean gestational age at delivery was 38.1 weeks in the pessary group compared to 37.8 weeks in the expectant management group, with no significant differences in the rates of delivery before 28, 34 or 37 weeks of gestation.

Currently, no published RCT compared the efficacy of the cervical pessary with that of cerclage or progestogens for short cervix in singletons or twins. A retrospective comparison between the methods has shown no significant differences in the rates of perinatal loss, neonatal morbidity or PTB for singleton pregnancies (apart from higher rate of PTB at <34 weeks' gestation in the vaginal progesterone vs the pessary group).

In 2003, the first case control study in twin pregnancies and cervical pessary was conducted. Twenty-three women with short cervical length (<25 mm) prior to 24 weeks of gestation were treated with pessary and matched with 23 controls. The mean gestational age at delivery was 35+6 weeks in the pessary group and 33+2 weeks in the control group (p value=0.02).

A large RCT published in 2013 included 403 women with twin pregnancies who were randomized to either prophylactic pessary or expectant management. Women with all cervical length were included. The authors concluded that prophylactic use of pessary in unselected twin pregnancies did not prolong pregnancy or reduce poor perinatal outcome. However, in a sub group analysis of women with a cervical length less than 38 mm (<25th percentile), a significantly lower incidence of poor neonatal outcomes, delivery before 32 weeks, and neonatal mortality was found in the pessary group.